Chandra

1
Chandras Influence on
Indian Astronomy

• Jayant V. Narlikar
• Inter-University Centre for Astronomy and
  Astrophysics, Pune , India

2
Chandra on Himself

• After the early preparatory years, my scientific
  work has followed a certain pattern motivated,
  principally, by a quest after perspectives.this
  quest has consisted in my choosinga certain area
  

which appears amenable to cultivation and
compatible with my taste, abilities and
temperament. And when after some years of study,
I feel that I have accumulated a sufficient body
of knowledge and achieved a view of my own, I
have the urge to present my point of view, ab
initio, in a coherent account with order, form
and structure
3
Seven periods in Chandras life

• 1. Stellar structure
• An Introduction to the Study of Stellar
  Structure
• (1939)

2. Stellar dynamics Principles of Stellar
Dynamics (1943)
3. Theory of radiative transfer Radiative
Transfer (1950)
4
Seven periods in Chandras life

• 4. Hydrodynamic and Hydromagnetic Instability
• Hydrodynamic and Hydromagnetic Stability
• (1961)

5. Equilibrium and stability of ellipsoidal
figures of equilibrium Ellipsoidal figures
of equilibrium (1968)
5
Seven periods in Chandras life

• 6. The General Theory of relativity
• The Mathematical theory of black holes
• (1983)

7. Newtons Principia Newtons Principia for
the Common Reader (1995)
6
The Indian Academia in the 20th Century

• Pre-independence (lt1947)
• Main centres of research were in the
  universities
• Astrophysics in physics departments
• Allahabad University (Meghnad Saha)
• Delhi University (Daulat Singh Kothari)
• Relativity and cosmology in maths departments
• Calcutta University (Nikhil Ranjan Sen)
• Benares Hindu University (V. V. Narlikar)

7

• Post-independence (gt1947)
• The emphasis on research shifted to autonomous
  research institutes (ARIs)
• Today AA research is done mainly in these
  institutions
• Mumbai TIFR
• Bangalore IIA, RRI, IISc
• Pune NCRA, IUCAA
• Ahmedabad PRL
• Naini Tal ARIES

Only IUCAA belongs to the university sector.
8
Chandra and Saha

• January 1930 meeting during
• the annual Indian Science Congress

Quote from Kameshwar Walis book A few
months later, 2-8 January 1930, Chandra attended
the Indian Science Congress Association meeting
held in Allahabad
9
Chandra and Saha

• .The host and the president of the physics
  section of the Congress was Meghnad Saha, the
  eminent Indian astrophysicist, whose theory of
  ionization a decade earlier had unlocked the door
  to the interpretation of stellar spectra in terms
  of laboratory spectra of atoms of terrestrial
  elements, providing information about the state
  of stellar atmospheres, their chemical
  composition, the density distribution of various
  elements, and then about the most important
  physical parameter the temperature

10
Chandra and Saha

• ...Chandra had learned all of this from
  Eddingtons book The Internal Constitution of
  Stars and was aware of the high esteem Eddington
  had accorded to Saha and of Sahas election to
  the Royal Society in 1927. But Chandra was not
  aware that Saha was acquainted with his own work
  so when he met Saha at the Congress and
  introduced himself, he was pleasantly surprised
  by Sahas compliment on his paper in the
  Proceedings of the Royal Society. Saha said that
  it was very suggestive and that one of his
  students was working on extending Chandras
  ideas.

11
Chandra and Saha

• He introduced Chandra to this student, who also
  seemed to know about his work, and he invited
  Chandra to his home for lunch with a small group
  of research workers all older than Chandra. The
  small lunch turned later into a dinner invitation
  with such distinguished senior Indian scientists
  as J.C. Ghosh, D.M. Bose, and J.N. Mukherjee.
  Saha persuaded Chandra to extend his stay in
  Allahabad so that he and his students could
  discuss more with him. Chandra, so young, did
  not expect to be treated almost as an equal by an
  internationally renowned scientist of Sahas
  stature.

Bose (centre) with students front row  Meghnad
Saha, J.C. Ghosh, back row S. Dutta, S.N. Bose,
D.M. Bose, N.R. Sen, J.N. Mukherjee and N.C. Nag
12
Kothari in Delhi

• Dense objects can be ionized at high pressure
  (instead of at high temperature)
• Eddington we only gradually came to realize
  that ionization could be produced by high
  pressure as well as high temperature. I think the
  first man to state this explicitly was
  D.S.Kothari...

13
Arnold Sommerfeld

• It is noteworthy that the Indian D.S. Kothari
  has developed an audacious relationship between
  the old fashioned planets and the now discovered
  newest heavenly bodies, the white dwarfs.
• Simulate planetary matter by keeping low
  temperature and high pressure.
• ?cold body cannot have radius more than that
  of planet Jupiter

14
Interaction with VVN

• The Vaidya solution in 1943 demonstrated that it
  is possible to use general relativity to describe
  a spherical object emitting energy in the form of
  radiation travelling with the speed of light
• P.C. Vaidya in Current Science, 12, 183, 1943
• His supervisor (V.V. Narlikar) asked Chandra if
  GR will have solutions to offer for astrophysics

15
Chandra and VVN

• Chandra replied No. He did not believe
  that situations relating to strong gravity would
  be found in astrophysics.
• For strong gravity we need
• a 2GM /c 2R ? 1.

16

• This can be achieved at modest masses provided
  the density is high and at modest densities
  provided
• the mass is high
• a (32p /3)1/3GM 2/3?1/3 ?
  1
• c 1
• The discovery of neutron stars and QSOs
  showed that such objects may well exist in the
  universe and so a new subject Relativistic
  Astrophysics was born
• Chandras lack of belief in the impact of GR
  at that stage matched Eddingtons disbelief that
  Nature would permit black holes

17
Benares Hindu University

• Dr S. Radhakrishnan, the VC at BHU had conveyed
  through VVN an offer to Chandra to head a new
  observatory which would be set up by the
  industrial house of the Birlas
• under the control of BHU.
• Chandra declined because he was not sure that
  the academic environment at BHU would continue
  once its distinguished VC left.
• His reservations were borne out

18
Osmania University

• Saleh Mohammed Alladin at Osmania had been a
  graduate student at the University of Chicago and
  in 1959 had attended the lectures by Chandra. He
  writes Professor Chandrasekhar used to
  emphasize that mathematical work should not only
  be correct, but should also be elegantly
  expressed
• The episode at Osmania which led to Alladins
  appointment
• Chandras help to K.D. Abhyankar in telescope
  site selection and on his work on radiative
  transfer.

19
Chandras Indian Graduate Students

• Chandra had two students from India who got their
  Ph.D. under him
• 1. S.K. Trehan (now deceased)
• 2. Bimla Buti
• Trehan had joined the Panjab University at
  Chandigarh and set up a school on theoretical
  hydrodynamics and plasma physics in the Applied
  Maths Dept

20

• Bimla Buti recalls
• Since Chicago University required single-author
  papers for a Ph.D. thesis, she had no joint
  papers with Chandra. Chandra had, however, helped
  on various occasions. She recalls his traits as
  follows.
• He was an extremely disciplined person and
  expected discipline around him

21

• Without fail he would visit the library and
  glance through the latest journals
• He was extremely hard workingHowever, he would
  find time for gardening, musical concerts,
  reading classic novels
• he was particular about English grammar
• He had a terrific memory . At a social gathering,
  he would narrate stories about his interactions
  with other scientists
• I found him very friendly and affectionate

22
The Sun and the Neutron Stars

• Chandras work on white dwarfs set the trend for
  stars made of degenerate matter, e.g., neutron
  stars.
• S.M. Chitre and V. Canuto and considered
  equations of state for neutron-dominated matter
  in a highly compressed formlead to maximum mass
  of the order of 2 solar masses.

23

• Stability of solar models was discussed by Chitre
  using Chandras perturbation technique. The
  eigenfrequencies so obtained were compared with
  the observed acoustic modes. The solar model can
  thus be made more precise to Compare the neutrino
  flux
• The conclusion was that the reduced flux has to
  do with neutrino physics and not with the solar
  model

24
Antonov Instability

• Discovered by Antonov in 1962.
• Padmanabhan saw that Chandra had discussed a
  similar situation back in 1939.
• Equations of stellar structure as written by him
  for an isothermal sphere reduce to a first order
  differential equation using variables u and v.
  Solutions are shown on a spiral curve in u,v
  plane.

25

• Paddy found that
• q RE / GM 2
• R radius, E energy and M mass
• Relates to Antonov instability. Q const.
• Are straight lines in u-v plane. If these
• Lines meet, there is Antonov instability.
• Did Chandra know this result back in 1939?
• Correspondence and direct meeting with
• Chandra failed to get him interested in the
• same problem 50 years later.

26

• Encounter with Ramanath Cowsik
• At a radio interview question on how one should
  approach the study of physics through
  experiments or through a study of theoretical
  physics?
• Chandra replied Different students approach
  physics in their own unique ways. But what is
  important is that they dedicate themselves to
  academic life

It does not matter through which gate one enters
a garden. Once you are in, you may wander
enjoying a bloom here or a bough there
27

• Chandras talk at IUCAA dedication The Series
  Paintings of Claude Monet and the Landscape of
  General Relativity drew parallels between
  aesthetics of paintings and Mathematical
  equations.

28
My first encounter with Chandra

• 1962 GR3 Conference in Jablonna, near Warsaw.
• In my morning walk I came across an Indian
  delegate neatly dressed in a dark suit who
  introduced himself as Chandrasekhar

29

• What was an astrophysicist doing at the GR
  meeting? I wondered

Chandra replied I am thinking of getting into
general relativity as my next research area. As I
am new to the subject, I decided to attend this
conference so that I may assess for myself what
are the interesting problems in this field.
30

• This was a reply from a young man of over 50.